ChBg is for changing desktop backgrounds in a given period. It can render images with 10 modes (such as tiled, centered, scaled, etc.). It uses Imlib1, Imlib2, or gdk_pixbuf for loading images, so it supports many image formats. ChBg has a windowed setup program, is able to load setup files, can be used as slideshow picture previewer in its own window or as a desktop background, and can be used as screensaver or as an xscreensaver hack. It has a dialog for fast previewing of pictures and very usable thumbnail previews.

matrix_saver is a console screen saver for FreeBSD. It is
based on Chris Allegretta's "cmatrix" which, in turn, was
based on the "code" effect in the movie "The Matrix." The net
effect is a cross between a code listing and rain falling on
a window pane.

Xautolock monitors console activity under the X window system, and fires up a program of your choice if nothing happens during a user configurable period of time. You can use this to automatically start up a screen locker in case you tend to forget to do so manually before having a coffee break.

xlockmore is an enhanced version of xlock. It incorporates several new commandline options, which allow you to run it in a window, in the root window, in a different size/location, change the size of the iconified window, to install a new colormap and delay locking for use with xautolock.

XScreenSaver is the standard screen saver
collection shipped on most Linux and Unix systems
running the X11 Window System. These screen savers
also work on Mac OS (X11 is not required). More
than 200 screen savers are included.

Snow Path Formation Simulator is a program that models the process of people forming very distinct, and yet not always altogether logical looking, paths in the snow as they walk across open spaces. The evolving condition of the snow is displayed graphically. This project may eventually mature into a screensaver.